JP2000146814A - Grain size distribution measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grain size measuring device capable of being used free of maintenance for a long time in any environments by making the structure of a measuring optical system strong against dust and humidity. SOLUTION: In this device, laser light 19 from a laser light source part 7 is radiated to a group of dispersed grains, scattered light 19A, 19B then produced is detected by a plurality of photodetectors 21, 24 to 29, and grain size distribution of the group of grains is measured based on scattered-light intensity signals from the respective photodetectors 21, 24 to 29. The laser light source part 7 is placed in an environment isolated from the outside air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for irradiating a dispersed particle group with laser light from a laser light source unit, detecting scattered light generated at that time by a plurality of photodetectors, and scattered light from each photodetector. The present invention relates to an apparatus for measuring a particle size distribution in the particle group based on an intensity signal.

[0002]

2. Description of the Related Art In a conventional particle size distribution measuring apparatus, an optical seal is provided for its measuring optical system, but a non-sealed type is generally used. FIG. 4 schematically shows a configuration of a measurement optical system in a conventional particle size distribution measuring apparatus. In this figure, reference numeral 41 denotes a sample liquid 42 in which a particle group to be measured is dispersed in an appropriate dispersion medium. This is a cell made of a transparent container. Reference numeral 43 denotes a laser light source unit provided on one side of the cell 41, a laser light source 44 composed of a He-Ne laser, mirrors 46 and 47 for changing the traveling direction of parallel laser light 45 from the laser light source 44, and a mirror 4
Beam expander 4 for expanding laser beam 45 passing through 6, 47
Consists of eight. The laser light source 43 is housed in a simple box 49 for providing an optical seal, and the laser beam 4 is applied to a portion of the box 49 facing the beam expander 48.
A hole 50 for allowing the passage of the air through the hole 5 is provided.

Reference numeral 51 denotes a condensing lens provided on the other side of the cell 41, and reference numeral 52 denotes a ring detector provided at a focal position of the condensing lens 51.
This is to detect scattered light and transmitted light generated when the particles inside are illuminated.

[0004]

However, in the measuring optical system of the particle size distribution measuring device having the above structure, the laser light source 43 is simply housed in the case 49 for providing a light seal. When the particle size distribution measuring device is installed in a place where dust and humidity are high, that is, where the device environment is inferior, moisture, dust and the like enter the laser light source unit 43 from the outside, and deteriorate the mirrors 46 and 47, or Stain the optical surface. When the mirrors 46 and 47 are provided with an optical axis adjustment alignment mechanism (not shown),
The components of the optical axis adjustment alignment mechanism are similarly deteriorated or soiled. Therefore, conventionally, when the particle size distribution measuring device is installed in the above-described environment, it is necessary to periodically perform maintenance such as cleaning and pay close attention to the maintenance.

The present invention has been made in consideration of the above-mentioned matters, and an object of the present invention is to provide a measuring optical system having a structure that is robust against dust and moisture, so that it can be used for a long time in any environment. An object of the present invention is to provide a particle size distribution measuring device that can be used without maintenance.

[0006]

In order to achieve the above object, according to the present invention, a laser beam from a laser light source is irradiated to a dispersed particle group, and scattered light generated at that time is detected by a plurality of photodetectors. In a device configured to measure a particle size distribution in the particle group based on a scattered light intensity signal from each photodetector, the laser light source unit is in an environment in which the laser light source unit is shielded from outside air.

In the above particle size distribution measuring apparatus, since the laser light source section including the optical equipment including the laser light source is in an environment in which the laser light source section is shielded from the outside air, the optical equipment can be protected not only from the light seal but also from dust and moisture. And the particle size distribution measuring device can be used for a long period of time without any maintenance even in a severe environment.

In the above particle size distribution measuring apparatus, the laser light source may be housed in a case having a closed structure having a window through which laser light passes, and the case may be filled with a dry gas. Item 2).

[0009]

1 to 3 show one embodiment of the present invention. FIG. 1 schematically shows the structure of a particle size distribution measuring apparatus according to the present invention. Is a perspective view showing an example of an optical bench in the particle size distribution measuring device, and FIG. 3 is a view schematically showing a plan configuration of the optical bench.

First, in FIGS. 1 and 2, reference numeral 1 denotes a flow-type cell comprising a transparent container for accommodating a sample solution 2 in which particles to be measured are dispersed in an appropriate dispersion medium. It is detachably and vertically supported between a cell holding block 5 mounted on a base member 4 provided on the upper surface and a cell cover block (not shown). Reference numeral 6 denotes an inlet for the sample liquid 2 formed in the cell holding block 5.

Reference numeral 7 denotes a laser light source unit provided on one side (rear side) of the cell 1 and is constructed as follows.
First, reference numeral 8 denotes a case made of, for example, a metal having a light-blocking and airtight structure, and a lower case 9 mounted on the upper surface of the optical bench base 3 and having a pentagonal shape in plan view, and a lower case 9 from above. An upper case 10 is detachably mounted. On the side wall of the case 8 facing the cell 1 of the upper case 9, for example, a window 11 made of a material through which laser light passes is formed in a sufficiently sealed state, and the lower end of the upper case 10 is formed. A seal member such as packing is provided between the upper case 9 and the upper end of the lower case 9.
The space formed by 0 and 9 is configured to be kept airtight.

Reference numerals 12 and 13 denote a gas inlet and a gas outlet provided in the upper case 10. Although not shown, the gas inlet 12 has an on-off valve and a drying gas (for example, a gas such as nitrogen gas). A gas supply line with a source or the like is connected, and a gas outlet 13 is provided.
Is connected to a gas discharge line provided with a check valve, a vacuum pump, and the like.

The following members are provided in the case 8 having the above-described sealing structure. That is, reference numeral 14 denotes a laser light source, which is made of, for example, a semiconductor laser, and is held on a light source substrate 15 erected in the lower case 9 so as to emit laser light in a horizontal direction. Reference numeral 16 denotes a condenser lens that converges divergent laser light emitted from the laser light source 14, and is held by a lens holding member 17 erected on the lower case 9. Reference numeral 18 denotes a converged laser beam that has passed through the condenser lens 16 (hereinafter, referred to as a converged laser beam) 19
Is held at the auto-alignment mechanism 20 by a mirror which is bent by 90 ° and reflects in the cell 1 direction. The signal lines and power supply lines for each of the above members housed in the case 8 can be introduced or led out of the case 8 through a connector of a type that can be hermetically sealed, or The surroundings are caulked with a silicone adhesive or the like.

1 to 3, reference numeral 21 denotes a ring detector provided on the other side (front side) of the cell 1, which is provided at a position where the focused laser beam 19 passing through the cell 1 is focused. I have. The ring detector 21 includes a plurality of photosensors each having a ring-shaped or semi-ring-shaped light-receiving surface having a radius different from each other with the optical axis of the condensed laser beam 19 as a center. The light 19A scattered / diffracted at a relatively small angle of the condensed laser light 19 diffracted or scattered by the light beam is received at each scattering angle, and the light intensity is measured. Reference numeral 22 denotes a preamplifier that amplifies the outputs of the photosensors constituting the ring detector 21.

In the vicinity of the cell 1, the light 19B scattered / diffracted at a relatively large angle among the condensed laser light 19 diffracted or scattered by the particles in the cell 1 is individually detected for each scattering angle. A wide-angle scattered light detection group 23 is provided. The wide-angle scattered light light detection group 23 includes a plurality of photosensors 24 to 29 provided at different angles from the ring detector 21, and a predetermined angle exceeding a predetermined angle due to particles in the cell 1 according to each arrangement angle. Angle scattered light 19B can be detected,
27 detect forward scattered light, the photo sensor 28 detects side scattered light, and the photo sensor 29 detects back scattered light. Reference numeral 30 denotes a preamplifier that amplifies the output of each of the photosensors 24 to 29.

Reference numeral 31 denotes a light shielding member provided on the front side of the wide-angle scattered light detection group 23, that is, on the front side of each of the photosensors 24 to 29, more specifically, on the light incident side. In the embodiment, it is composed of two plate members 32 and 33 erected in parallel with each other. These plate members 32 and 33 are made of, for example, a thin stainless steel plate that does not transmit light. And these plate members 32, 33
As shown in FIG. 2 and FIG.
A plurality of openings, for example, slits 34 and 35 for passing only scattered light 19B having a specific scattering angle with respect to.
Have been established by methods such as etching. For example, the slits 34 and 35 corresponding to one photosensor 24 that detects forward scattered light are not necessarily the same shape and size, and only the scattered light 19B having a predetermined scattering angle out of the forward scattered light from the cell 1 is used. The mutual positions are set so as to be incident on the photo sensor 24. This means that the slits 3 corresponding to the other photo sensors 25 to 29
The same applies to 4 and 35.

Referring again to FIG. 1, reference numeral 36 denotes a multiplexer for sequentially taking in the outputs from the plurality of amplifiers 22 and 30 and sequentially sending the outputs to the AD converter 37. Reference numeral 38 denotes an operation to which the output of the AD converter 37 is input. A computer as a processing device. The computer 38 outputs the digital signals converted from the ring detector 24 and the outputs of the photosensors 24 to 29 (digital data relating to light intensity).
Is stored based on the Fraunhofer diffraction theory or the Mie scattering theory, and a program for obtaining a particle size distribution in a particle group is stored.

In the particle size distribution measuring apparatus constructed as described above, the upper case 10 is attached to the lower case 9 in which the laser light source unit 7 is disposed to form a sealed case 8, and in this state, the case 8 is sealed. The air inside the case 8 is discharged by operating a vacuum pump of a gas discharge line connected to the gas discharge port 13 provided in the gas discharge port 8. Thereby, the water vapor inside the case 8 is discharged. Thereafter, the dry gas is supplied to the case 8 through a gas supply line connected to the gas inlet 12.
The inside of the case 8 is supplied with a dry gas.

In this state, when the sample liquid 2 is supplied to the cell 1 and a laser beam is emitted from the laser light source 14, this laser beam is converged by the condenser lens 16 and the condensed laser beam 1
9, the sample liquid 2 in the cell 1 is irradiated via the mirror 18. The condensed laser light 19 is diffracted or scattered by the particles in the cell 1. Of the diffracted light or scattered light, the light 19A having a relatively small scattering angle is imaged on the ring detector 21. In this case, the photosensor disposed on the outer peripheral side emits light having a larger scattering angle. Upon receiving the light, the inner-side photosensor receives light having a smaller scattering angle. Therefore, the light intensity detected by the photosensor on the outer peripheral side reflects the amount of particles having smaller particle diameters, and the light intensity detected by the photosensor on the inner peripheral side reflects the amount of sample particles having larger particle diameters. You are doing. The light intensity detected by each of these photosensors is converted into an analog electric signal, and further input to the multiplexer 36 via the preamplifier 19.

On the other hand, of the condensed laser light 19 diffracted or scattered by the particles, one 19B having a relatively large scattering angle is provided on the front side (light incident side) of the wide-angle scattered light light detection group 23. The scattered light 19B having a specific scattering angle is limited by the slits 34 and 35 formed in the plate members 32 and 33, respectively, and is incident on the photosensors 24 to 29, respectively, and the light intensity distribution thereof is measured. In this case, scattered light from particles having a large particle size is detected in the order of the forward scattered light photosensors 24 to 27, the side scattered light photosensor 28, and the back scattered light photosensor 29. The light intensity detected by each of the photosensors 24 to 29 is converted into an analog electric signal, and further input to the multiplexer 36 via the preamplifier 30.

In the multiplexer 36, measurement data from the ring detector 21 and the photosensors 24 to 29, that is, analog electric signals are sequentially taken in a predetermined order. Then, the analog electric signal captured by the multiplexer 36 is converted into a serial signal,
The digital signals are sequentially converted into digital signals by the D converter 37 and further input to the computer 38.

The computer 38 processes the light intensity data for each scattering angle obtained by the ring detector 21 and the photo sensors 24-29 based on the Fraunhofer diffraction theory or Mie scattering theory.

As described above, in the above particle size distribution measuring device, the light intensity distribution of the scattered light in the particle size range with a large particle diameter is measured by the ring detector 21 and the light intensity distribution in the particle size range with a small particle size is measured. The light intensity distribution of the wide-angle scattered light is measured by the photo sensors 24 to 29, and the outputs of the ring detector 21 and the photo sensors 24 to 29 are processed by the computer 38. Can be obtained all at once in a wide range from a relatively large particle size to a very small particle size.

In the above-mentioned particle size distribution measuring apparatus, the laser light source unit 7 composed of the laser light source 14, the condenser lens 16, the mirror 18, and the optical equipment such as the auto alignment mechanism 20 for holding the mirror 18 shuts off the outside air. Since the laser light source unit 7 is housed in the case 8 in which the dry gas is sealed, the laser light source unit 7 is placed not only in an optical seal but also in an environment that is shielded from the outside air. The optical device can be protected from dust and moisture as well as a light seal against the laser light. Therefore, the laser emitting surface of the laser light source 14, both surfaces of the condenser lens 16, the reflecting surface of the mirror 18, and the auto alignment mechanism 20 can be protected. Dust and moisture do not adhere to the parts. Therefore, it is not necessary to periodically clean these optical members, and the optical members can be used for a long period of time without any maintenance even in a severe environment, and the reliability of the device is greatly improved.

In the above-described embodiment, the laser light source section 7 centering on the laser light source 14 is in an environment in which the laser light source section 7 is isolated from the outside air. However, if necessary, the cell 1, the ring detector 21, and the photo sensors 24 to 29 may be used. About
You may make it the state cut off from the outside air.

In the case 8, it is not always necessary to provide a gas outlet, and the internal pressure in the case 8 may be increased.

As the laser light source 14, another laser such as a He-Ne laser may be used instead of the semiconductor laser. Then, the laser light 1 focused on the cell 1
Instead of irradiating the cell 9, the cell 1 may be irradiated with a parallel laser beam as shown in FIG. In this case, it is necessary to provide a condenser lens (a lens indicated by reference numeral 51 in FIG. 4) between the cell 1 and the ring detector 21.

Further, the cell 1 does not need to be of a flow type, and the object of measurement is not only particles in a liquid, but also powders and particles dispersed in a gas, powders and granules in a solid, and the like. There may be.

[0029]

According to the present invention, since the laser light source section is in an environment in which the laser light source section is shielded from the outside air, the optical device can be protected from dust and moisture as well as the optical seal, and even in a severe environment. In addition, the particle size distribution measuring device can be used for a long period without maintenance, and the reliability of the device is improved.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a configuration of a particle size distribution measuring device of the present invention.

FIG. 2 is a perspective view showing an example of an optical bench of the particle size distribution measuring device.

FIG. 3 is a diagram schematically showing a planar configuration of the optical bench.

FIG. 4 is a diagram schematically showing a configuration of a conventional particle size distribution measuring device.

[Explanation of symbols]

7: Laser light source unit, 8: Case, 11: Window, 19: Laser light, 19A, 19B: Scattered light, 21, 24 to 29: Photodetector.

Claims (2)

[Claims] 1. A method for irradiating a dispersed particle group with laser light from a laser light source unit, detecting scattered light generated at that time by a plurality of photodetectors, and detecting the scattered light based on a scattered light intensity signal from each photodetector. An apparatus for measuring a particle size distribution in a particle group, wherein the laser light source section is placed in an environment that is shielded from outside air. 2. The particle size distribution measuring apparatus according to claim 1, wherein the laser light source section is housed in a case having a closed structure having a window through which the laser light passes, and a dry gas is sealed in the case. .